Technical Brief

Thermal Annealing Effect on the Optical, Electrical and Morphological Properties of the PBTTT-C12:PC71BM Blend Films

[+] Author and Article Information
Karwan Wasman Qadir

Low Dimensional Material Research Centre,
Department of Physics,
University of Malaya,
Kuala Lumpur 50603, Malaysia;
Department of Physics,
College of Education,
Salahaddin University—Hawler,
Erbil 44001, Kurdistan Region, Iraq

Zubair Ahmad

Low Dimensional Material Research Centre,
Department of Physics,
University of Malaya,
Kuala Lumpur 50603, Malaysia
e-mail: zubairtarar@um.edu.my

Khaulah Sulaiman

Low Dimensional Material Research Centre,
Department of Physics,
University of Malaya,
Kuala Lumpur 50603, Malaysia

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received June 3, 2014; final manuscript received November 21, 2014; published online January 15, 2015. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 137(3), 034503 (Jun 01, 2015) (4 pages) Paper No: SOL-14-1166; doi: 10.1115/1.4029230 History: Received June 03, 2014; Revised November 21, 2014; Online January 15, 2015

We investigate the effect of thermal annealing on the optical, morphological and photovoltaic (PV) properties of bulk heterojunction (BHJ) solar cell based on the poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C12) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM). The ITO/PEDOT:PSS/PBTTT-C12:PC71BM/Al devices were fabricated on glass substrates from the PBTTT-C12:PC71BM (1:4) solution in dichlorobenzene. Atomic force microscopy (AFM) is used to investigate the surface morphology of the PBTTT-C12:PC71BM thin films. The AFM results show that the thin film’s surface roughness decreases with increasing annealing temperature, making the annealed films smoother as compared to the nonannealed sample. The efficiency of the ITO/PEDOT:PSS/PBTTT-C12:PC71BM/Al PV devices increased from 1.85% to 2.48% with an increase in temperature from 0 °C to 150 °C.

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Grahic Jump Location
Fig. 1

Molecular structure of poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C12) (a) and [6,6]-phenyl C71butyric acid methyl ester (PC71BM) (b).

Grahic Jump Location
Fig. 2

(a) Absorption spectra of the PBTTT-C12 and PBTTT-C12:PC71BM blend as a function of annealing temperature in the visible light spectrum regions. (b) PL spectra of the blend films a function of annealing temperature. Inset in (b) shows the PL spectrum of the PBTTT-C12 pristine thin film on glass.

Grahic Jump Location
Fig. 3

AFM images of the PBTTT-C12:PC71BM (1:4) thin films on ITO coated glass substrates, (a) nonannealed, (b) annealed at 50 °C, (c) annealed at 100 °C, and (d) annealed at 150 °C.

Grahic Jump Location
Fig. 4

J–V characteristics of ITO/PEDOT:PSS/PBTTT-C12:PC71BM/Al BHJ solar cells annealed at different temperatures.



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